I. Field of the Invention
This invention relates to novel imide polymers and to methods for preparation thereof.
II. Description of the Prior Art
The basic reaction of formation of imides by reacting ammonia, butylamine, dodecyl amine or octyl amine with polymethyl methacrylate is shown in Graves U.S. Pat. No. 2,146,209, German Pat. No. 1,077,872 and German Pat. No. 1,242,369. Schroder et al U.S. Pat. No. 3,284,425 and British Pat. No. 926,629 show a route toward imidized acrylics by reacting polymethyl methacrylate with ammonium hydroxide, ammonium phosphate, alkyl amines or a combination of partial reaction with ammonium hydroxide followed by reaction with alkyl amine. British Pat. No. 1,045,229 shows chemical modification of methacrylic acid/methacrylonitrile (MMA/MAN) copolymers or terpolymers by heating at 180.degree.-300.degree. C. to give the cyclic amide product, optionally with a dispersing solvent. German Pat. Nos. 1,247,517; 2,041,736; and 2,047,096 show methacrylamide/methyl methacrylate (MAN/MMA) copolymers, inert solvent, and heat to achieve imide formation accompanied by evolution of ammonia. Most prior patents and literature on processes to imidized acrylics via reaction of ammonia and primary amines with polymethyl methacrylates, U.S. Pat. No. 3,284,425 for example, are directed to an autoclave batch process requiring lengthy heating time, usually 7 hours or more, in the presence of inert dissolving or suspending solvent. U.S. Pat. No. 3,557,070 describes a process for preparing ethylene/methacrylic acid/methacrylamide terpolymers from an ethyleneisopropyl methacrylate copolymer by heating the copolymer to the decomposition temperature (325.degree. C.) of the isopropyl ester to form methacrylic anhydride units which are then reacted with gaseous ammonia to give methacrylamide and methacrylic acid residues in the polymer chain. The reaction is run neat without solvent and the patent examples mention decomposition "zones". Although this patent does not mention that these reactions are taking place in an extruder, the Derwent abstract of this patent mentioned that these reactions may be run in an extruder. The use of extruders as polymer reactors has been shown as a route to copolyesters (Preparation and Properties of Copolyesters Polymerized in a Vented Extruder, J. Applied Polymer Science 12,2403[1968], nylon products (Direct Extrusion of Nylon product from Lactams, Modern Plastics, August 1969--Warner Pfleiderer) and graft polymerization of polyolefins (Steinkamp et al U.S. Pat. No. 3,862,265). West German Pat. No. 1,077,872 discloses an extruder process of imidizing acrylic polymers using a water solution of ammonia, but the product is a foamed strand with deficient thermal stability and which requires further processing before it can be used to fabricate useful items; furthermore, the process described is not commercially feasible in that the foamed polymer exits the extruder under high pressure with free ammonia vapor.
It is an object of the present invention to provide a process for imidization of acrylic polymers at low residence times. It is a further object to provide a process for imidization of acrylic polymers without substantial molecular weight degradation and wherein the polymers produced have a high, uniform molecular weight and are non-crosslinked and thermoplastic, and have improved thermal stability. A further object is to provide a process wherein less than substantially complete imidization of acrylic polymers is possible, especially to produce uniformly imidized polymers.
Another object is to provide novel imidized acrylic polymers. A still further object is to provide an improved process for producing imide polymers with improved properties, free of the disadvantages of prior processes.